Priority is claimed to Korean Patent Application No. 10-2004-0022036, filed on Mar. 31, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a robot, and more particularly, to an anthropomorphic robot having two legs and capable of walking upright.
2. Description of the Related Art
In robots, one of important conditions required for a foot of a robot is that it provide an effective interaction between the ground and the foot of the robot. When the heel of a foot of the robot touches the ground, a shock is generated and the shock is transferred to the body of the robot through ankle of the foot of the robot. Such a shock may break dynamic equilibrium of the robot so that walking becomes unstable for the robot. Also, the shock generated when the heel of a foot of the robot touches the ground may cause vibration to the foot of the robot. The vibration is transferred to the body of the robot, which makes control of the robot difficult.
Another problem relating to the walking of the robot are that small obstacles exist on the ground in an activity area of an actual environment, which cannot be recognized by a vision system of the robot and is not included in the control of the robot, is not so flat as a 2 dimensional plane.
Accordingly, due to the obstacle and uneven activity area, the foot of the robot steps on a position different from that originally calculated with no consideration of them. As a result, the walking motion of the robot becomes unstable and the movement is not smooth.
A widely known anthropomorphic robot, for example, P2, HRP, or WABIAN, has a foot formed of two metal parts connected by an elastic adapter. A shock absorption mechanism for the foot of the anthropomorphic robot consists of four rubber bushes inserted in guides. When a force is transferred from a base plate to the four rubber bushes, the four rubber bushes are elastically deformed in a vertical direction. Further, the four rubber bushes mechanically act as a low pass filter so that vibration can be prevented during a compliance control process with respect to legs of the robot.
However, since the above conventional foot of the robot has a constant stiffness, it is very inconvenient to step on the ground or off from the ground. Moreover, the foot of the robot is very sensitive to small obstacles existing on the ground or a small uneven area. In other words, a capacity of the robot reacting to the small obstacles existing on the ground or small uneven area is deteriorated.